Field of Invention
The present invention relates to a hole saw assembly, especially to a hole saw assembly that includes a drill rod able to be mounted in and released from a hole saw quickly. The drill rod is generally fixed in an axial hole of the hole saw and is applied to hole saws with different diameters used as a shaft for positioning. Thus the hole saw will not have offset during rotation.
Description of Related Arts
In a conventional hole saw assembly, a drill rod can be quickly changed from the hole saw by a quick release device. The design of most of the quick release devices is for hole saws with larger diameter (such as hole saws with the diameter larger than 30 mm). For example, refer to U.S. Pat. No. 8,328,474, a quick change arbor, a hole cutter and a method suitable for hole saws with high torsion and large diameter are revealed. A hole cutter 12 includes an end plate 14. A drive shank 24 includes a body portion 26 with flats 25. The flats 25 are fastened on the end plate 14 while the pilot bit 64 is arranged at the drive shank 24. The body portion 26 is assembled with a collar 50 to form the quick change pilot bit 64. The quick change device is connected to the drive shank 24 and is having drive pins 36 set on the end plate 14 and driven into the corresponding drive pin apertures 18. The hole cutter 12 uses the drive shank 24 as a main transmission shaft. However, such structure is unable to be applied to hole saws with diameter smaller than 30 mm. This is due to that the width of the contact surface of the hole saws with the diameter smaller than 30 mm is unable to be assembled with the drive pins 36.
Refer to Canadian Pat. No. 2283453, an extractor is revealed. The extractor is applied to hole saws with small diameter. An adaptor is axially movable along a drill rod so as to remove debris attached on a hole saw and the drill rod. The drill rod is unable to be released from the adaptor. When the drill rod gets damaged, the drill rod and the adaptor should be replaced together. The adaptor is axially moved and then a head part of the drill rod is positioned by radial rotation. The adaptor is against and locked by a spring. After being used for a period of time, the spring may undergo elastic fatigue and the adaptor is unable to be locked and positioned on the position required. This results in that the head part of the drill rod is unable to be positioned and moved axially. This is dangerous for the users during the operation because the head part may be biased and get broken. Thus the drill rod is unable to be used as a positioning shaft of the hole saw.
For overcoming shortcomings of the conventional devices, reducing offset of the drill rod and quick change of the drill head from the hole saw, there is a need to provide a novel hole saw assembly that includes a quick release device designed for hole saws with diameter no more than 30 mm.